U.S. Pat. No. 3,056,684 teaches protective paintlike coatings containing powdered zinc and partially hydrolyzed ethyl silicate. Several brands of zinc-rich coatings utilizing partially hydrolyzed ethyl silicate are commercially available. Typically, these zinc-rich coatings employ other pigments besides zinc dust to (1) lower costs, (2) enhance appearance or (3) improve performance. Because the desired pigments are not soluble in the system, they must be dispersed to their optimum particle size.
Dispersion of the pigments directly in the ethyl silicate binder would jeopardize product stability as well as require dedication of special manufacturing equipment. However, if dispersion of these pigments could be carried out in a solvent compatible with the hydrolyzed ethyl silicate these problems can be eliminated. The dispersed pigment/solvent blend could be added to the hydrolyzed ethyl silicate binder solution just prior to packaging without compromising product stability nor requiring dedication of equipment. But, it is not possible to disperse the desired pigments in the solvents because the pigments are not soluble in the solvents. A means was needed to create the shear-viscosity condition necessary for proper pigment dispersion.